Host Buffer Multiplier

[tommymandel]

Hey Frodo, maybe this one's for you, and James, I did do a search, but got a lot of peripheral hints at an answer, but no answer to my specific question, namely:

2007-2008 Intel 8-core 3ghz, E-SATA card for Audio drive, internal SATA drive for VI's and Libraries, 2x 24io's (PCI-E), plus 1x Digidesign 002R.

I now seem to get a great deal better Audio Performance Bar Graph when I set it to
256, 4x Host Buffer.

Now I'm reading that latency is the product of those 2 numbers, and (an earlier Frodo post) that the older Intel machines had a slower FW bus.

And also that the host buffer multiplier should reflect how many (different?) audio drivers (in my case, 2: Digicore and Motu PCI-E) are in use.

As I'm only bringing 4 channels, max, of audio in or out of the FW (Digi002R) bus at any time, is my 256, 4x Host Buffer the way I should be configuring?

Thanks ! ! !

[tommymandel]

(Talking to yerself again, Tommy? )

I wish the DP 7 User Manual had a more comprehensive index. Couldn't find Host Buffer or Multiplier in it. I finally found a reference to the Getting Started Guide. I could only locate my v.5 Getting Started Guide, but even so, now understand that Host Buffer Multiplier is not for multi cores, it's for extending your Buffer Settings to greater numbers, and for Multiple Audio Drivers (in my case, the PCI 424 and the DigiCore drivers). Accordingly, in the absence of real glitching, I should keep mine at 2, unless I want to introduce more latency, which I could just as easily do by changing the Audio Buffer setting to 512 (I guess it's actually been equal to 1024 since I've set it to 256 with 4x Host Buffer Multiplier - no wonder the Audio Performance bar was so wonderfully low!)
And it was good to read that "Digital Performer takes full advantage of multi-processor Macintosh computers." (regardless of Audio System Config settings.)

[tommymandel]

NOW, I find this

Hey there!

I've just read through the thread and I seem to be missing the discussion of WHY you want large buffer settings. I assume the question is: what is the best optimization? The answer is: That depends on how you are using DP, and what computer and audio interfaces you have.

The Buffer Size describes the size of the sample packets that are sent from the interface driver into DP, through DP, and back out DP to the driver again. A smaller Buffer Size means a lower-latency patch through for audio signals, as well as trigger to output time for virtual instruments. The lower Buffer Size also means the computer does more tasks over the same period of time (greater CPU load).

It's common practice to use a smaller Buffer Size when patching through or triggering live instruments, and a larger Buffer Size when you are doing complex mixes.

The available sizes of the buffer that you see in the DP Hardware Driver window are the result of what the driver makes available. It's possible that different Buffer Sizes may be available at different sample rates.

The Buffer Multiplier is a DP setting that allows you to multiply the driver buffer setting. If the driver is set to 1024 and you set the multiplier to 2, DP is now using a buffer size of 2048.

Running more than one audio driver at a time is more load for the computer. Therefore, raising the Buffer Size that DP is processing may help with efficiency.

It is common advice (but not an absolute requirement) to use the Buffer Multiplier if you are running multiple audio drivers.

The other parameter that comes into play here is Work Priority. Work Priority changes DPs thread priority within the OS in relation to the audio driver. A lower setting means the audio driver can get higher thread priority. The Medium or Low setting can be useful on older G4 and G5 Macs, and can be useful when using some non-MOTU audio interfaces.

You'll notice I'm using phrases like "may be" and "can be". That's because there are no absolute best settings. As a matter of fact, very large buffer settings and very low Work Priority settings can have an adverse effect. There is a point of diminishing returns and the fact is, at some point all that data has to be processed, regardless of buffer packet size.

So that means you may need to do some testing to find the optimum settings for your particular configuration.

Dave

[Licornerouge]

Hello all ! here's a hint & question using host buffer multiplier
I'm running high definition audio projects 88.2 Khz with 3xHD192 and 1x2408mkIII on one PCIe 424 Card.
Generally up to 24 Tracks recording + multiple playback tracks at the same time. We recently added SSD Drives to our system - Mac Pro "Quad Core" 3.2 (2012)
Everything was running fine then doing guitar overdubs, we suddenly had issues with cracks in the audio signal that appeared after recording (we do not monitor our tracks through the interfaces or through the software, so we figured that after the recording)
Our settings then, were 1024 smp per buffer (I now assume that in 88.2 Khz this certainly was a bit hard on the processor & on the drives)
We sitched back to the old SATA internal drives and managed to free the maximum space inside... same problem...

So we decided to switch to 2x buffer multiplier and then things seems to run fine now, but we are in the middle of the project and still have more & more tracks to record, I think this is gonna Be up to 3-4 simultaneous record enabled tracks + 40 or 48 tracks of playback for each song, maybe more.

The point : setting host buffer multiplier to 2x seemed to work fine for the moment, but if I have new issues, will 4x or 8x do the job ?
What are your thoughts ?
Thanks in advance
Ted

[Robert Randolph]

Hello all ! here's a hint & question using host buffer multiplier
I'm running high definition audio projects 88.2 Khz with 3xHD192 and 1x2408mkIII on one PCIe 424 Card.
Generally up to 24 Tracks recording + multiple playback tracks at the same time. We recently added SSD Drives to our system - Mac Pro "Quad Core" 3.2 (2012)
Everything was running fine then doing guitar overdubs, we suddenly had issues with cracks in the audio signal that appeared after recording (we do not monitor our tracks through the interfaces or through the software, so we figured that after the recording)
Our settings then, were 1024 smp per buffer (I now assume that in 88.2 Khz this certainly was a bit hard on the processor & on the drives)
We sitched back to the old SATA internal drives and managed to free the maximum space inside... same problem...

So we decided to switch to 2x buffer multiplier and then things seems to run fine now, but we are in the middle of the project and still have more & more tracks to record, I think this is gonna Be up to 3-4 simultaneous record enabled tracks + 40 or 48 tracks of playback for each song, maybe more.

The point : setting host buffer multiplier to 2x seemed to work fine for the moment, but if I have new issues, will 4x or 8x do the job ?
What are your thoughts ?
Thanks in advance
Ted

If you're not monitoring through DP, you may as well use whatever the highest buffer size you feel comfortable with.

The only downside is there will be a slight lag between when you change a control (fader) and when you hear the result. It's relatively minor even at high settings, but it's worth keeping in mind.

[Shooshie]

As regards the Host Buffer Multiplier, the general rule is 1X per driver. If you are using, say, three audio interfaces, and each requires its own driver, you'd use a buffer multiplier for each one, thus 3X. If you are using 3 similar boxes with the same driver (say, 3 MOTU 896 MK3, or 3 MOTU PCI or 3 AVB boxes) you'd only use 1X, because there is just one driver controlling all 3.

That's how I learned it, anyway. If Dave were to tell it differently, I'd go with Dave's version, but I think he's the one I learned it from.

Shooshie

[HCMarkus]

Hello all ! here's a hint & question using host buffer multiplier
I'm running high definition audio projects 88.2 Khz with 3xHD192 and 1x2408mkIII on one PCIe 424 Card.
Generally up to 24 Tracks recording + multiple playback tracks at the same time. We recently added SSD Drives to our system - Mac Pro "Quad Core" 3.2 (2012)
Everything was running fine then doing guitar overdubs, we suddenly had issues with cracks in the audio signal that appeared after recording (we do not monitor our tracks through the interfaces or through the software, so we figured that after the recording)
Our settings then, were 1024 smp per buffer (I now assume that in 88.2 Khz this certainly was a bit hard on the processor & on the drives)
We sitched back to the old SATA internal drives and managed to free the maximum space inside... same problem...

So we decided to switch to 2x buffer multiplier and then things seems to run fine now, but we are in the middle of the project and still have more & more tracks to record, I think this is gonna Be up to 3-4 simultaneous record enabled tracks + 40 or 48 tracks of playback for each song, maybe more.

The point : setting host buffer multiplier to 2x seemed to work fine for the moment, but if I have new issues, will 4x or 8x do the job ?
What are your thoughts ?
Thanks in advance
Ted

Give your Mac a boost... buy one of these and drop it in, if not now, when you finish the current project:

http://www.ebay.com/itm/Intel-W3690-Xeo ... SwOVpXbZnZ

almost as fast, considerably cheaper:

http://www.ebay.com/itm/Intel-Xeon-W368 ... SwEjFXcdSq

As far as going b beyond 2x, per Magic Dave:

...very large buffer settings and very low Work Priority settings can have an adverse effect. There is a point of diminishing returns and the fact is, at some point all that data has to be processed, regardless of buffer packet size.

Read his post above for the gory details.

[mikehalloran]

So we decided to switch to 2x buffer multiplier and then things seems to run fine now, but we are in the middle of the project and still have more & more tracks to record, I think this is gonna Be up to 3-4 simultaneous record enabled tracks + 40 or 48 tracks of playback for each song, maybe more

No. You never need all tracks playing back when overdubbing new ones. Save that for the mix.

At lower buffer sizes, DP may not play back all tracks. Depending on your settings, you may also induce distortion or glitches due to CPU overload. Make it easy on yourself and decide which guide tracks are necessary and enable those only during overdub sessions. When done, raise the buffer to whatever setting works best and do your mix.

[SMS]

So we decided to switch to 2x buffer multiplier and then things seems to run fine now, but we are in the middle of the project and still have more & more tracks to record, I think this is gonna Be up to 3-4 simultaneous record enabled tracks + 40 or 48 tracks of playback for each song, maybe more

No. You never need all tracks playing back when overdubbing new ones. Save that for the mix.

At lower buffer sizes, DP may not play back all tracks. Depending on your settings, you may also induce distortion or glitches due to CPU overload. Make it easy on yourself and decide which guide tracks are necessary and enable those only during overdub sessions. When done, raise the buffer to whatever setting works best and do your mix.

Or do a quick bounce or freeze of all the tracks and just overdub to that stereo stem.

[bayswater]

As regards the Host Buffer Multiplier, the general rule is 1X per driver. If you are using, say, three audio interfaces, and each requires its own driver, you'd use a buffer multiplier for each one, thus 3X. If you are using 3 similar boxes with the same driver (say, 3 MOTU 896 MK3, or 3 MOTU PCI or 3 AVB boxes) you'd only use 1X, because there is just one driver controlling all 3.

That's how I learned it, anyway. If Dave were to tell it differently, I'd go with Dave's version, but I think he's the one I learned it from.

Shooshie

That's what I remember but Getting Started now says to try 2 for multiple drivers if and when there are audio glitches, rather than matching the number of drivers.